The file containing the source code shown below is located in the corresponding directory in <sdk>/samples/android-<version>/...
/*
* Copyright (C) 2007 The Android开源工程
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package com.example.android.apis.graphics.spritetext;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Paint.Style;
import android.graphics.drawable.Drawable;
import android.opengl.GLUtils;
import java.util.ArrayList;
import javax.microedition.khronos.opengles.GL10;
import javax.microedition.khronos.opengles.GL11;
import javax.microedition.khronos.opengles.GL11Ext;
/**
* An OpenGL text label maker.
*
*
* OpenGL labels are implemented by creating a Bitmap, drawing all the labels
* into the Bitmap, converting the Bitmap into an Alpha texture, and drawing
* portions of the texture using glDrawTexiOES.
*
* The benefits of this approach are that the labels are drawn using the high
* quality anti-aliased font rasterizer, full character set support, and all the
* text labels are stored on a single texture, which makes it faster to use.
*
* The drawbacks are that you can only have as many labels as will fit onto one
* texture, and you have to recreate the whole texture if any label text
* changes.
*
*/
public class LabelMaker {
/**
* Create a label maker
* or maximum compatibility with various OpenGL ES implementations,
* the strike width and height must be powers of two,
* We want the strike width to be at least as wide as the widest window.
*
* @param fullColor true if we want a full color backing store (4444),
* otherwise we generate a grey L8 backing store.
* @param strikeWidth width of strike
* @param strikeHeight height of strike
*/
public LabelMaker(boolean fullColor, int strikeWidth, int strikeHeight) {
mFullColor = fullColor;
mStrikeWidth = strikeWidth;
mStrikeHeight = strikeHeight;
mTexelWidth = (float) (1.0 / mStrikeWidth);
mTexelHeight = (float) (1.0 / mStrikeHeight);
mClearPaint = new Paint();
mClearPaint.setARGB(0, 0, 0, 0);
mClearPaint.setStyle(Style.FILL);
mState = STATE_NEW;
}
/**
* Call to initialize the class.
* Call whenever the surface has been created.
*
* @param gl
*/
public void initialize(GL10 gl) {
mState = STATE_INITIALIZED;
int[] textures = new int[1];
gl.glGenTextures(1, textures, 0);
mTextureID = textures[0];
gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID);
// Use Nearest for performance.
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MIN_FILTER,
GL10.GL_NEAREST);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_MAG_FILTER,
GL10.GL_NEAREST);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_S,
GL10.GL_CLAMP_TO_EDGE);
gl.glTexParameterf(GL10.GL_TEXTURE_2D, GL10.GL_TEXTURE_WRAP_T,
GL10.GL_CLAMP_TO_EDGE);
gl.glTexEnvf(GL10.GL_TEXTURE_ENV, GL10.GL_TEXTURE_ENV_MODE,
GL10.GL_REPLACE);
}
/**
* Call when the surface has been destroyed
*/
public void shutdown(GL10 gl) {
if ( gl != null) {
if (mState > STATE_NEW) {
int[] textures = new int[1];
textures[0] = mTextureID;
gl.glDeleteTextures(1, textures, 0);
mState = STATE_NEW;
}
}
}
/**
* Call before adding labels. Clears out any existing labels.
*
* @param gl
*/
public void beginAdding(GL10 gl) {
checkState(STATE_INITIALIZED, STATE_ADDING);
mLabels.clear();
mU = 0;
mV = 0;
mLineHeight = 0;
Bitmap.Config config = mFullColor ?
Bitmap.Config.ARGB_4444 : Bitmap.Config.ALPHA_8;
mBitmap = Bitmap.createBitmap(mStrikeWidth, mStrikeHeight, config);
mCanvas = new Canvas(mBitmap);
mBitmap.eraseColor(0);
}
/**
* Call to add a label
*
* @param gl
* @param text the text of the label
* @param textPaint the paint of the label
* @return the id of the label, used to measure and draw the label
*/
public int add(GL10 gl, String text, Paint textPaint) {
return add(gl, null, text, textPaint);
}
/**
* Call to add a label
*
* @param gl
* @param text the text of the label
* @param textPaint the paint of the label
* @return the id of the label, used to measure and draw the label
*/
public int add(GL10 gl, Drawable background, String text, Paint textPaint) {
return add(gl, background, text, textPaint, 0, 0);
}
/**
* Call to add a label
* @return the id of the label, used to measure and draw the label
*/
public int add(GL10 gl, Drawable drawable, int minWidth, int minHeight) {
return add(gl, drawable, null, null, minWidth, minHeight);
}
/**
* Call to add a label
*
* @param gl
* @param text the text of the label
* @param textPaint the paint of the label
* @return the id of the label, used to measure and draw the label
*/
public int add(GL10 gl, Drawable background, String text, Paint textPaint,
int minWidth, int minHeight) {
checkState(STATE_ADDING, STATE_ADDING);
boolean drawBackground = background != null;
boolean drawText = (text != null) && (textPaint != null);
Rect padding = new Rect();
if (drawBackground) {
background.getPadding(padding);
minWidth = Math.max(minWidth, background.getMinimumWidth());
minHeight = Math.max(minHeight, background.getMinimumHeight());
}
int ascent = 0;
int descent = 0;
int measuredTextWidth = 0;
if (drawText) {
// Paint.ascent is negative, so negate it.
ascent = (int) Math.ceil(-textPaint.ascent());
descent = (int) Math.ceil(textPaint.descent());
measuredTextWidth = (int) Math.ceil(textPaint.measureText(text));
}
int textHeight = ascent + descent;
int textWidth = Math.min(mStrikeWidth,measuredTextWidth);
int padHeight = padding.top + padding.bottom;
int padWidth = padding.left + padding.right;
int height = Math.max(minHeight, textHeight + padHeight);
int width = Math.max(minWidth, textWidth + padWidth);
int effectiveTextHeight = height - padHeight;
int effectiveTextWidth = width - padWidth;
int centerOffsetHeight = (effectiveTextHeight - textHeight) / 2;
int centerOffsetWidth = (effectiveTextWidth - textWidth) / 2;
// Make changes to the local variables, only commit them
// to the member variables after we've decided not to throw
// any exceptions.
int u = mU;
int v = mV;
int lineHeight = mLineHeight;
if (width > mStrikeWidth) {
width = mStrikeWidth;
}
// Is there room for this string on the current line?
if (u + width > mStrikeWidth) {
// No room, go to the next line:
u = 0;
v += lineHeight;
lineHeight = 0;
}
lineHeight = Math.max(lineHeight, height);
if (v + lineHeight > mStrikeHeight) {
throw new IllegalArgumentException("Out of texture space.");
}
int u2 = u + width;
int vBase = v + ascent;
int v2 = v + height;
if (drawBackground) {
background.setBounds(u, v, u + width, v + height);
background.draw(mCanvas);
}
if (drawText) {
mCanvas.drawText(text,
u + padding.left + centerOffsetWidth,
vBase + padding.top + centerOffsetHeight,
textPaint);
}
// We know there's enough space, so update the member variables
mU = u + width;
mV = v;
mLineHeight = lineHeight;
mLabels.add(new Label(width, height, ascent,
u, v + height, width, -height));
return mLabels.size() - 1;
}
/**
* Call to end adding labels. Must be called before drawing starts.
*
* @param gl
*/
public void endAdding(GL10 gl) {
checkState(STATE_ADDING, STATE_INITIALIZED);
gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID);
GLUtils.texImage2D(GL10.GL_TEXTURE_2D, 0, mBitmap, 0);
// Reclaim storage used by bitmap and canvas.
mBitmap.recycle();
mBitmap = null;
mCanvas = null;
}
/**
* Get the width in pixels of a given label.
*
* @param labelID
* @return the width in pixels
*/
public float getWidth(int labelID) {
return mLabels.get(labelID).width;
}
/**
* Get the height in pixels of a given label.
*
* @param labelID
* @return the height in pixels
*/
public float getHeight(int labelID) {
return mLabels.get(labelID).height;
}
/**
* Get the baseline of a given label. That's how many pixels from the top of
* the label to the text baseline. (This is equivalent to the negative of
* the label's paint's ascent.)
*
* @param labelID
* @return the baseline in pixels.
*/
public float getBaseline(int labelID) {
return mLabels.get(labelID).baseline;
}
/**
* Begin drawing labels. Sets the OpenGL state for rapid drawing.
*
* @param gl
* @param viewWidth
* @param viewHeight
*/
public void beginDrawing(GL10 gl, float viewWidth, float viewHeight) {
checkState(STATE_INITIALIZED, STATE_DRAWING);
gl.glBindTexture(GL10.GL_TEXTURE_2D, mTextureID);
gl.glShadeModel(GL10.GL_FLAT);
gl.glEnable(GL10.GL_BLEND);
gl.glBlendFunc(GL10.GL_SRC_ALPHA, GL10.GL_ONE_MINUS_SRC_ALPHA);
gl.glColor4x(0x10000, 0x10000, 0x10000, 0x10000);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glPushMatrix();
gl.glLoadIdentity();
gl.glOrthof(0.0f, viewWidth, 0.0f, viewHeight, 0.0f, 1.0f);
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glPushMatrix();
gl.glLoadIdentity();
// Magic offsets to promote consistent rasterization.
gl.glTranslatef(0.375f, 0.375f, 0.0f);
}
/**
* Draw a given label at a given x,y position, expressed in pixels, with the
* lower-left-hand-corner of the view being (0,0).
*
* @param gl
* @param x
* @param y
* @param labelID
*/
public void draw(GL10 gl, float x, float y, int labelID) {
checkState(STATE_DRAWING, STATE_DRAWING);
Label label = mLabels.get(labelID);
gl.glEnable(GL10.GL_TEXTURE_2D);
((GL11)gl).glTexParameteriv(GL10.GL_TEXTURE_2D,
GL11Ext.GL_TEXTURE_CROP_RECT_OES, label.mCrop, 0);
((GL11Ext)gl).glDrawTexiOES((int) x, (int) y, 0,
(int) label.width, (int) label.height);
}
/**
* Ends the drawing and restores the OpenGL state.
*
* @param gl
*/
public void endDrawing(GL10 gl) {
checkState(STATE_DRAWING, STATE_INITIALIZED);
gl.glDisable(GL10.GL_BLEND);
gl.glMatrixMode(GL10.GL_PROJECTION);
gl.glPopMatrix();
gl.glMatrixMode(GL10.GL_MODELVIEW);
gl.glPopMatrix();
}
private void checkState(int oldState, int newState) {
if (mState != oldState) {
throw new IllegalArgumentException("Can't call this method now.");
}
mState = newState;
}
private static class Label {
public Label(float width, float height, float baseLine,
int cropU, int cropV, int cropW, int cropH) {
this.width = width;
this.height = height;
this.baseline = baseLine;
int[] crop = new int[4];
crop[0] = cropU;
crop[1] = cropV;
crop[2] = cropW;
crop[3] = cropH;
mCrop = crop;
}
public float width;
public float height;
public float baseline;
public int[] mCrop;
}
private int mStrikeWidth;
private int mStrikeHeight;
private boolean mFullColor;
private Bitmap mBitmap;
private Canvas mCanvas;
private Paint mClearPaint;
private int mTextureID;
private float mTexelWidth; // Convert texel to U
private float mTexelHeight; // Convert texel to V
private int mU;
private int mV;
private int mLineHeight;
private ArrayList<Label> mLabels = new ArrayList<Label>();
private static final int STATE_NEW = 0;
private static final int STATE_INITIALIZED = 1;
private static final int STATE_ADDING = 2;
private static final int STATE_DRAWING = 3;
private int mState;
}